Ribbed sign holder clamp



FIG. 1 is a front elevational view of a ribbed sign holder clamp showing my new design which is a mirror image of the rear elevational view;

FIG. 2 is a right side elevational view;

FIG. 3 is a top plan view;

FIG. 4 is a bottom plan view;

FIG. 5 is a front perspective view; and,

FIG. 6 is a left side elevational view. 

The ornamental design for a ribbed sign holder clamp, as shown and described. 